A known seat apparatus for a vehicle is movable between a seating position and a stowed position so as to increase a passenger capacity, a space for luggage, and the like. For example, JP2005-126035A (corresponding to U.S. Pat. No. 6,935,682) (hereinafter referred to as Reference 1) discloses a sinking seat for a vehicle that includes catch legs at a lower front portion of a seat cushion and grooved legs at a lower rear portion of the seat cushion. Each of the legs is engageable and disengageable relative to a floor. The seat apparatus is configured to be locked at the seating position by means of the four legs. The seat apparatus is stowed within a concave portion formed at the floor in such a manner that a seatback is folded on the seat cushion by means of lower portions of rear legs rotatable relative to the floor. The rear legs also include upper portions respectively that are integrally connected to the grooved legs. In addition, a vehicle seat disclosed in JP2006-264586A (hereinafter referred to as Reference 2) includes left and right front legs supporting a front portion of a cushion frame and left and right rear legs supporting a rear portion of the cushion frame. Each of the front legs and each of the rear legs are connected to each other by means of a stranded cable. The front legs and the rear legs are rotatable relative to the cushion frame. When the vehicle seat is stowed, each of the legs rotates to be accommodated within a space formed at a floor by means of the stranded cable and other mechanisms, so that the vehicle seat is compactly stowed.
Further, US2003-0184129A1 (hereinafter referred to as Reference 3) discloses a seat for a vehicle including a hinge mechanism provided at one side surface of a seat cushion (seat base) and two legs provided at a lower side of the other side surface of the seat cushion. Specifically, the two legs are arranged at front and rear portions of the lower side of the other side surface. When the seat rotates upward about the hinge mechanism while a seatback is folded on the seat cushion, the seat is stowed sideways. When the seat rotates downward from the stowed position and the legs engage with respective strikers (engagement members), the seat is brought to a seating position.
As mentioned above, according to the mechanism where the seat is locked at the seating position by means of the four legs or of the hinge mechanism and the two legs, lock devices are generally provided at lower ends of the respective legs while the strikers (engagement members) for engagement with the respective lock devices are provided at a vehicle floor.
According to the structure including the four legs disclosed in Reference 1 and Reference 2, while the seat is moving from the stowed position to the seating position, the last fourth lock device may not successfully engage with the striker even when the three lock devices engage with the respective strikers. More specifically, members constituting the lock device and the strikers each may have a manufacturing tolerance. In addition, variations in positional relationship caused when the members are mounted may occur. Thus, operation timings of the four lock devices possibly vary. The lock device that operates first is not influenced by operations of the other three lock devices and thus easily engages with the striker. The following second and third lock devices are able to engage with the respective strikers because the position of the seat is not yet fixed. However, after the first to third lock devices engage with the respective strikers, the seat is locked at three points and thus the position of the seat is restricted. Then, positions of the remaining fourth lock device and the corresponding striker may not match each other, which leads to an incomplete locking of the seat at the seating position. In the same way, according to the structure including the hinge mechanism and the two legs disclosed in Reference 3, the first lock device that is operated first successfully engages with the striker, however, the second lock device may unsuccessfully engage with the striker.
In a case where even only one of the lock devices incompletely engages with the corresponding striker, the stability of the seat in the seating position deteriorates.
The operations of the lock devices may vary from each other because of not only an initial factor such as dimensions and a mounting position of each component but also a time-dependent factor such as abrasion and deformation of the component caused by a frequent use.
A need thus exists for a seat apparatus for a vehicle which is not susceptible to the drawback mentioned above.